Semiconductor processing typically involves fabrication of devices, such as transistors, diodes, and integrated circuits, upon a thin piece of semiconductor material called a substrate. The semiconductor processing takes place in a reaction region, where gases are passed over the substrate, resulting in a controlled deposit of material upon the substrate. The substrate is lifted into the reaction region by a susceptor.
FIG. 1 illustrates such a prior art reaction system 100. The reaction system 100 includes a reaction region 105 and a substrate loading region 110. The reaction region 105 is defined by a reaction region housing 115 and a reactant distribution system 120. The reactant distribution system 120 is illustrated as a showerhead gas flow system, but could be a cross-flow designed system. Separating the reaction region 105 and the substrate loading region 110 is a baseplate 125. A substrate chamber housing 130 defines the substrate loading region 110.
In FIG. 1, the reaction system 100 is in a substrate loading mode, as a substrate 135 is loaded on top of a susceptor 140. The susceptor 140 is moved up and down by a movement element 145. The movement element 145 may also allow rotation of the susceptor 140 and the substrate 135. Also, a substrate loading mechanism 150 is configured to load and unload the substrate 135 onto the susceptor 140.
Disposed at various points along the susceptor 140 are a set of pads 155. The pads 155 are disposed between the susceptor 140 and the baseplate 125. The pads prevent direct physical contact between the susceptor 140 and the baseplate 125.
FIG. 2 illustrates the reaction system 100 in a substrate processing mode. The substrate 135 is moved into the reaction region 105 by the susceptor 140 and the movement element 145. When the reaction system 100 is in the substrate processing mode, the pad 155 in the susceptor 140 will contact the baseplate 125.
FIG. 3 shows a zoomed view of the contact between the pad 155 and the baseplate 125. A gap 160 is formed between the susceptor 140 and the baseplate 125 during processing of substrate 135. The purpose of the gap 160 is to allow fluid communication between the inside of the reaction region and outside the susceptor. A height 165 of the pads 155 can range between 0.001 inches (approximately 25 μm) and about 0.05 inches (approximately 1275 μm). When the pad 155 contacts the baseplate 125, the gap 160 will be the height of the pad 155 that is above a susceptor surface 140A.
Over time, continued processing in the reaction region 105 can result in a deposition of reactive materials on and around the pads 155 of the susceptor 140. This deposition build-up can lead to the reduction in size of the gap 160. As a result, the build-up may change the flow dynamics inside and outside the reaction region 105. This can cause issues of contamination and defects in the processed substrate 135.
In addition, continued contact between the pads 155 and the baseplate 125 may result in an erosion of the pads 155. As shown in FIG. 3A, a result of the continued contact is a reduction in a height 165′ of the pads 155 as well as a reduction in a gap 160′. The flow dynamics inside and outside the reaction region 105 will be affected.
One course of action exists to deal with the deposition build-up. The reaction region may be opened and the pads may be replaced. In addition, the reaction region itself may be replaced. However, with these steps, the reaction region may be disassembled. The disassembly would take place after a particular number of cycles or substrates processed. This number was determined through the use of historical data that monitored how the deposition build-up of materials occurred. The disassembly is generally not feasible as it leads to processing downtime.
As a result, it is desired to have an arrangement for the reaction region to address the issue of a shrinking gap due to build-up without the disassembly of the reaction region.